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© 2004 British Nutrition Foundation

Nutrition Bulletin

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Blackwell Science, LtdOxford, UKNBUNutrition Bulletin1471-98272004 British Nutrition Foundation

? 2004

29

2111142

Briefing Paper

Nutritional aspects of cerealsBrigid McKevith

Correspondence:

Brigid McKevith, Nutrition Scientist, British Nutrition Foundation, High Holborn House, 52–54 High Holborn, London WC1V 6RQ, UK. E-mail: [email protected]

BRIEFING PAPER

Nutritional aspects of cereals

Brigid McKevith

British Nutrition Foundation, London, UK

SUMMARY1 INTRODUCTION

1.1 General structure of grains1.2 Wheat1.3 Rice1.4 Maize1.5 Barley1.6 Oats1.7 Rye1.8 Millet1.9 Sorghum1.10 Triticale1.11 Other grains1.12 Key points

2 TECHNICAL ASPECTS OF CEREALS

2.1 Cereal production2.2 Storage2.3 Processing2.4 Cereals and food safety2.5 Key points

3 THE ROLE OF CEREALS IN HEALTH AND DISEASE

3.1 History of cereals in diet3.2 Nutritional value of cereals3.3 Contribution of cereals and cereal products in the diet3.4 Cereals in health and disease3.5 Labelling and health claims3.6 Consumer understanding3.7 Key points

4 FUTURE DEVELOPMENTS

4.1 Fortification4.2 Genetic modification4.3 Gene–nutrient interactions4.4 Key points

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5 CONCLUSIONS AND RECOMMENDATIONSREFERENCESGLOSSARY

Summary

Cereals are the edible seeds or grains of the grass family, Gramineae. A number ofcereals are grown in different countries, including rye, oats, barley, maize, triticale,millet and sorghum. On a worldwide basis, wheat and rice are the most importantcrops, accounting for over 50% of the world’s cereal production. All of the cerealsshare some structural similarities and consist of an embryo (or germ), which con-tains the genetic material for a new plant, and an endosperm, which is packed withstarch grains.

After harvest, correct storage of the grain is important to prevent mould spoilage,pest infestation and grain germination. If dry grains are held for only a few months,minimum nutritional changes will take place, but if the grains are held with a higheramount of moisture, the grain quality can deteriorate because of starch degradationby grain and microbial amylases (enzymes). Milling is the main process associatedwith cereals, although a range of other techniques are also used to produce a varietyof products. Slightly different milling processes are used for the various grains, butthe process can generally be described as grinding, sifting, separation and regrind-ing. The final nutrient content of a cereal after milling will depend on the extent towhich the outer bran and aleurone layers are removed, as this is where the fibre,vitamins and minerals tend to be concentrated. There is potential for contaminationof cereals and cereal products by pests, mycotoxins, rusts and smuts. Recently, acry-lamide (described as a probable carcinogen) has been found in starchy baked foods.No link between acrylamide levels in food and cancer risk has been established andbased on the evidence to date, the UK Food Standards Agency has advised the pub-lic not to change their diet or cooking methods. However, the Scientific Committeeon Food of the European Union (EU) has endorsed recommendations made by Foodand Agriculture Organisation/World Health Organization which include research-ing the possibility of reducing levels of acrylamide in food by changes in formula-tion and processing.

Cereals have a long history of use by humans. Cereals are staple foods, and areimportant sources of nutrients in both developed and developing countries. Cerealsand cereal products are an important source of energy, carbohydrate, protein andfibre, as well as containing a range of micronutrients such as vitamin E, some of theB vitamins, magnesium and zinc. In the UK, because of the mandatory fortificationof some cereal products (

e.g.

white flour and therefore white bread) and the vol-untary fortification of others (

e.g.

breakfast cereals), cereals also contribute signif-icant amounts of calcium and iron. Cereals and cereal products may also contain arange of bioactive substances and there is growing interest in the potential healthbenefits these substances may provide. Further research is required in this area,including identification of other substances within cereals and their bioavailability.

There is evidence to suggest that regular consumption of cereals, specificallywholegrains, may have a role in the prevention of chronic diseases such as coronary


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heart disease, diabetes and colorectal cancer. The exact mechanisms by which cere-als convey beneficial effects on health are not clear. It is likely that a number of fac-tors may be involved,

e.g.

their micronutrient content, their fibre content and/ortheir glycaemic index. As there may be a number of positive health effects associ-ated with eating wholegrain cereals, encouraging their consumption seems a pru-dent public health approach. To increase consumption of wholegrain foods, it maybe useful to have a quantitative recommendation. Additionally, a wider range ofwholegrain foods that are quick and easy to prepare would help people increasetheir consumption of these foods. As cereal products currently contribute a con-siderable proportion of the sodium intake of the UK population, manufacturersneed to continue to reduce the sodium content of foods such as breakfast cerealsand breads where possible.

Nutrition labelling is currently not mandatory in the UK, although many man-ufacturers provide information voluntarily. The fibre content of most UK foods isstill measured using the Englyst method rather than the American Association ofAnalytical Chemists (AOAC) method used by other EU countries and the USA.However, UK recommendations for fibre intake currently relate to fibre measuredby the Englyst method and not the AOAC method, and hence need revisions. EUchanges to labelling regulations will see the labelling of common foods and ingre-dients causing allergic reactions, including cereals containing gluten and productsderived from these foods. The introduction of EU legislation covering health claimsmay help consumers identify foods with proven health benefits.

Several misconceptions exist among the public with regard to cereals and cerealproducts. Firstly, many more people believe they have a food intolerance or allergyto these foods than evidence would suggest and, secondly, cereals are seen by someas ‘fattening’. The public should not be encouraged to cut out whole food groupsunnecessarily and, as cereals and cereal products provide a range of macro- andmicronutrients and fibre, eliminating these foods without appropriate support andadvice from a registered dietitian or other health professional could lead to prob-lems in the long term.

In the future it is possible that white flour in the UK may be fortified with folicacid (the synthetic form of the B vitamin folate) to decrease the incidence of neuraltube defects during pregnancy. Such a move could also be of benefit for heart health,as poor folate status is associated with high homocysteine levels, an emerging riskfactor for cardiovascular disease. However, high intakes of folic acid can mask vita-min B

12

deficiency, a condition that occurs more frequently with age and has seriousneurological symptoms affecting the peripheral nervous system.

Manipulating the expression of native genes can increase the disease resistance ofcereal crops. Novel genes may also be used for this purpose, as well as for developingcereals with resistance to herbicides, and cereals with improved nutritional prop-erties (

e.g.

increased levels of iron in cereals and of beta-carotene in rice). The long-term consequences and consumer acceptability of such advances must be consideredand consumer choice maintained. There is a continual growth in the knowledge ofthe interactions between human genes and nutrients, and in the future it may be pos-

sible to target specific nutrition messages to people with specific genetic profiles.

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1 Introduction

Cereals can be defined as a grain or edible seed of thegrass family, Gramineae (see Fig. 1) (Bender & Bender1999). Cereals are grown for their highly nutritious edi-ble seeds, which are often referred to as grains. Somecereals have been staple foods both directly for humanconsumption and indirectly via livestock feed since thebeginning of civilisation (BNF 1994). Cereals are themost important sources of food (FAO 2002), and cereal-based foods are a major source of energy, protein, Bvitamins and minerals for the world population. Gener-ally, cereals are cheap to produce, are easily stored andtransported, and do not deteriorate readily if kept dry.

1.1 General structure of grains (Fig. 2)

Grains develop from flowers or florets and, although thestructures of the various cereal grains are different, thereare some typical features. The

embryo

(or germ) is athin-walled structure, containing the new plant. It is sep-arated by the

scutellum

(which is involved in mobilisa-tion of food reserves of the grain during germination)from the main part of the grain, the

endosperm

. Theendosperm consists of thin-walled cells, packed with

starch grains. If the cereal grain germinates, the seedlinguses the nutrients provided by the endosperm until thedevelopment of green leaves that allow photosynthesisto begin (FAO 1991; Kent & Evers 1994). Theendosperm is surrounded by the

aleurone

, consisting ofone or three cell layers (wheat, rye, oats, maize and sor-ghum have one; rice and barley three). The outer layersof the grain are the pericarp (derived from the ovary ofthe flower) which surround the

seed coat

(the testa). Theouter thick-walled structures form the bran.

1.2 Wheat

Wheat is a major cereal crop in many parts of the world.It belongs to the Triticum family, of which there aremany thousands of species (Kent & Evers 1994), with

T. aestivum

subspecies Vulgare and the hard wheat

T. durum

being the most important commercially (Mac-rae

et al

. 1993). Wheat is grown as both a winter and aspring cereal and, owing to the number of species andvarieties and their adaptability, it is grown in manycountries around the world. The great wheat-producingcountries of the world include the USA, China andRussia; extensive wheat growing occurs in India,Pakistan, the European Union (EU), Canada, Argentinaand Australia. It is estimated that 556.4 million tonnesof wheat will have been produced in 2003, accountingfor 30% of the world’s cereal production (FAO 2003).

An ear or spike of grain is made up of spikelets (seeFig. 3a). The wheat grain is enclosed between the lemmaand the palea of each spikelet (see Fig. 3b). The grainmay be elliptical, oval or ovate in shape and have shortor long brush hairs. Most cultivated varieties of wheathave fusiform spikes, may be awned (bearded) or awn-less, and are easily threshed.

Wheat is generally not classed by variety. Insteadclasses are used, based on the time of year the wheat isgrown and the milling and baking quality of the flour

Figure 1

Taxonomy of the Gramineae family (source: Shewry

et al.

1992).

Family: Gramineae

Subfamily

Tribe

Genus

Oryzeae Triticeae Aveneae Paniceae Andropogonee Cynodonteae

Eleusine(Ragi)

SorghumPennisetum(Millet)

Avena(Oats)

Triticum(Wheat)

Oryza(Rice)

Secale(Rye)

Zea(Maize)

Coix(Job's tears)Hordeum

(Barley)

Figure 2

General structure of a grain (source:

Wheat: The Big Picture

(Dr Gary Barker, webmaster. [email protected]).

endosperm

aleurone layerseed coat scutellum

embryo shoot

embryo root

brush


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produced. Within each class there is a group of differentvarieties of wheat with similar characteristics. Most ofthe wheat produced is used for human consumption andbecause of its unique properties, a large range of ingre-dients and foods are produced, including wheat germ,spelt (a coarse type of wheat), couscous, cracked wheator bulgur and wheat starch.

1.3 Rice

Rice is an important crop, forming a staple food formany of the world’s population, especially those livingin Asia. Rice is produced mainly for use as human food,including breakfast cereals, and in Japan it is also usedto brew saké (Kent & Evers 1994). There is a huge num-ber of rice varieties (

~

100 000) but only a few are grownwidely (

e.g.

varieties of the improved semi-dwarf planttype with erect leaves). Cereal production within theEuropean Union is shown in Table 2.

The rice grain consists of an outer protective coating(referred to as the hull or husk) and the edible rice cary-opsis. Brown rice consists of the outer layers of pericarp(which contains pigment), seed coat, the embryo and theendosperm (comprising the aleurone layer whichencloses the embryo, subaleurone layer and the starchyor inner endosperm).

Wild rice is unrelated to rice. It is the grain of a NorthAmerican plant,

Zizania aquatica

, and, as it is difficultto harvest, is more expensive than other grains. It has ahigher protein content than rice (Bender & Bender1999).

1.4 Maize

Zea mays

L., also referred to as corn, originated in theWestern Hemisphere (Fast & Caldwell 2000). It is acheap form of starch and is a major energy source foranimal feed (Macrae

et al

. 1993). Although there arehundreds of different varieties, the four main categoriesof commercial importance are:

(1) dent maize (identified by the dent in the crown ofthe kernel);(2) flint maize (hard, round kernels);(3) sweet corn (a dent-type maize);(4) popcorn (flint-type maize which expands whenheated).

The maize kernel (the reproductive seed of the plant) hasfour main parts – the germ, the endosperm, the pericarpand the tip cap. Production in the USA exceeds that inany other country (Fast & Caldwell 2000) and muchresearch has been done in the USA on the maize genome(see section 4.2 for more on genetic modification).

Figure 3

(a) Ear of wheat (b) Wheat grain. (source: Wheat: The Big Picture (Dr Gary Barker, webmaster. [email protected]).

(b)

rachis

spikelet 5

spikelet 3

spikelet 1

spikelet 2

spikelet 4

spikelet 6

peduncle

floret 4floret 3

floret 1

floret 2

glume

rachilla

glume

palea

collar

(a)

lemmalodicules

starnens

carpul

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1.5 Barley

Barley is a resilient plant, tolerant of a range of condi-tions, which may have been cultivated since 15 000

BC

(Fast & Caldwell 2000). Cultivated barley,

Hordeumvulgare

, is mainly grown for animal feed, especially forpigs, for malting and brewing in the manufacture of beerand for distilling in whisky manufacture. A smallamount of barley is used for food. Pearled barley is eatenin soups and stews in the UK and in the Far and MiddleEast; barley is also used in bread (as flour) and groundas porridge in some countries (Kent & Evers 1994).

The barley head or spike is made up of spikelets,which are attached to the rachis in an alternating pat-tern. The outer layers of the barley kernel consist of ahusk, completely covering the grain; the pericarp (towhich the husk is tightly joined in most species); thetesta or seed coat and the aleurone.

1.6 Oats

Oats can grow well on poor soil and in cool, moist cli-mates and have mainly been grown for animal feed. Asmall proportion is produced for human consumption –oatmeal for porridge and oatcakes, rolled oats for por-ridge, and oat flour for baby foods and for ready-to-eat(RTE) breakfast cereals (Kent & Evers 1994). Oats arealso used in a range of non-food uses, including cosmet-ics and adhesives (Macrae

et al

. 1993).There are several different species, with the common

spring or white oat (

A. sativa

L

.

) being the most impor-tant cultivated form.

A. byzantina

is a red-oat typeadapted to warmer climates where it is grown as a win-ter oat. An oat spikelet consists of oat kernels. Each ker-nel is enclosed by a hull (made up of two layers – alemma and palea) which is only loosely attached to thegroat. The groat, which makes up 65–85% of the oatkernel, is enveloped by bran layers (pericarp, seed coatand aleurone cells).

1.7 Rye

Rye is a hardy plant and is generally grown in cool tem-perature zones, where other cereals can not be grown.Rye can also grow at high altitudes and in semi-aridareas. It is grown as a winter crop, being sown in earlyautumn and harvested in early summer. The plant mayvary in height from 30 cm to more than 2 m. It is amajor crop in Russia, Poland, Germany and the Scan-dinavian countries, where it is the major bread grain.Rye is also used to produce crispbread and alcohol, andit is used as animal feed (Kent & Evers 1994).

The grain is covered with a

glume

(husk), which is

normally bearded, and grains are arranged in an alter-nating pattern along the rachis. The grain is thinner andmore elongated than wheat; it is normally greyish-yellow in colour and varies in size from 1.5 mm to3.5 mm. The grain consists of the starchy endosperm(

~

86% of the grain), the pericarp and the testa (jointlyreferred to as the bran and accounting for 10% of thegrain), with the remainder consisting of the germ (theembryo and scutellum).

1.8 Millet

Millet refers to a number of different species, all ofwhich are small-grained, annual cereal grasses (Macrae

et al

. 1993; Bender & Bender 1999). The most impor-tant type is pearl millet. A number of minor millets exist,including finger (or ragi), proso and foxtail but as theseaccount for less than 1% of the grains produced forhuman consumption, they are less important in terms ofworld food production. However, these crops areimportant in certain locations in Africa and Asia, wheremajor cereals can not be relied on to provide sustainableyields (FAO 1995). Climatic and soil requirements,length of growing period, grain consistency, size andtaste differ depending on the species.

Job’s tears (Coix lachryma-jobi) is a type of milletwild grass, related to maize. It grows wild in parts ofAfrica and Asia, where its seeds (adlay) are eaten(Bender & Bender 1999).

1.9 Sorghum

Sorghum (

Sorghum bicolor

L. Moench) is a warm sea-son crop, intolerant of low temperatures but fairly resis-tant to serious pests and diseases. It is known by avariety of names (such as great millet and guinea corn inWest Africa, kafir corn in South Africa, jowar in Indiaand kaoliang in China) and is a staple food in manyparts of Africa, Asia, and parts of the Middle East. Mostof the sorghum produced in North and Central Amer-ica, South America and Oceania is used for animal feed(FAO 1995).

The grain consists of a naked caryopsis, made up of apericarp, endosperm and germ. Although there is a hugerange of physical diversity, sorghums are classed intoone of four groups – (1) grain sorghum; (2) forage sor-ghum; (3) grass sorghum; or (4) Sudan sorghums andbroomcorn (Macrae

et al

. 1993). Sorghums are groupedusing the following characteristics:

• the colour of the pericarp (white, yellow or red);• presence/absence of pigmented testa (with/withouttannins);


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• pericarp thickness;• endosperm colour (white, heteroyellow or yellow);• endosperm type (normal, heterowaxy or waxy).

1.10 Triticale

Triticale (full name Triticosecale) was the first cerealproduced by man by crossing wheat and rye. It has thewinter hardiness of rye and the baking properties ofwheat (Bender & Bender 1999). It is, however, suscep-tible to diseases which attack wheat and rye (Macrae

et al

. 1993). Triticale is used mainly as a feed crop but itcan be milled into flour and used to make bread,although adjustments are needed in recipe formulationbecause it does not have the same gluten content aswheat (Kent & Evers 1994).

1.11 Other grains

In addition to the cereals outlined above, there are sev-eral others which, although not important on a globallevel, may have an important role in certain parts of theworld. For example, buckwheat (also known as Saracencorn) is produced from the plant

Fagopyrum esculentum

and is eaten as a cooked grain, porridge or baked intopancakes. From the South American plant

Chenopo-dium album

comes the grain quinoa, which is used inChile and Peru to make bread (Bender & Bender 1999).

1.12 Key points

• There are many different types of cereals grownworldwide, each sharing some structural similarities.• Cereals are the grain or edible seed of plantsbelonging to the grass family and are very importantnutritionally.• Cereals consist of an embryo (or germ) which con-tains the genetic material for a new plant. The main partof the grain, is the endosperm, packed with starchgrains. If the cereal grain germinates, the seedling usesthe nutrients provided by the endosperm until the devel-opment of green leaves.

2 Technical aspects of cereals

Although various cereals are grown in different coun-tries depending on climatic conditions, wheat and riceare the most important cereals worldwide. Cereals aregrown for export as well as for domestic use and a num-ber of different processes are used. These processes canaffect the nutritional and technical properties of the endproduct.

2.1 Cereal production

Cereals are grown in a range of countries (Table 1). Theforecast for the world’s cereal production in 2003 is1865 million tonnes, 30% as wheat and 21% as milledrice. Over 50% of the world’s cereal is produced indeveloping countries (FAO 2003).

The total UK 2003 cereal harvest was an estimated22.3 million tonnes, with wheat and barley accountingfor about 66% and 30%, respectively, and oats account-ing for about 3.5% of the total cereal production(DEFRA & National Statistics 2003) (Table 2).

Table 1

Forecasts for cereal production in 2003 (million tonnes)

Area Wheat Rice (paddy)Coarse grains(all other grains)

Asia 245.6 541.0 211.4Africa 20.5 18.0 84.9Central America 3.0 2.4 29.1South America 22.0 19.5 76.0North America 83.3 8.9 302.3Europe 160.0 3.0 198.6Oceania 22.0 0.4 10.4World 556.4 396 912.8

Source: FAO 2003.

Table 2

Useable cereal produced and human consumption of cereals within the European Union for 2000/2001 (all figures are in 000 tonnes)

CountryUseable production2000/2001

Human consumption2000/2001

Belgium 2 246 1112Denmark 9 412 595Germany 45 219 8033Greece Data not available Data not availableSpain 23 475 4110France Data not available Data not availableIreland 2 383 472Italy 19 390 9822Luxembourg 154 41The Netherlands Data not available Data not availableAustria 4 498 849Portugal 1 484 1292Finland 4 089 538Sweden 5 669 841The UK 23 991 7409

Source: Eurostat 2002.

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2.2 Storage

After harvest, grains may either be temporarily stored onthe farm before being taken to a collection centre, or thegrains may go directly to a collecting centre. Grains arethen transported to larger storage facilities called coun-try elevators, which are filled with grain by rolling belts.

Although methods for maintaining the quality ofcereal grains have been in practice since ancient times,deterioration is seen even in countries with advancedtechnology (Chelowski 1991). Storage is associated witha range of hazards. Mould spoilage, pest infestations andgrain germination (which can occur if sufficient moistureis present,

e.g.

condensation can be produced in metallicbins) are the main problems (see section 2.4 about foodsafety issues for further information on these topics).Good storage is vital to minimise post-harvest losses andalthough moisture content is the most important prop-erty affecting stability of the grain during storage(Chelowski 1991), temperature and duration of storageare also important factors (Richard-Molard 2003).

An important step prior to storage is drying, toremove excess water from the grain (Table 3). A rangeof different types of driers may be used. High-tempera-ture driers are capable of drying large quantities of grainquickly but may also affect the grain if not used cor-rectly,

e.g.

thermal denaturing of the cereal’s proteinmay affect the properties of the final product. However,this method has the advantage of destroying insects.Natural drying methods have also been used,

e.g.

dryingcorncobs using wind and solar driers. Cereals can alsobe stored with higher water contents than usual in mod-ified atmospheres, but this is only appropriate when theend product is not required to have special properties

(

e.g.

to possess functional properties of bread). Exam-ples of modified atmosphere storage include under-ground storage and silos flushed with nitrogen. Thesestorage methods have the added advantage of killinginsects.

During storage there may be some nutritional changesto the cereals, although for dry grains these changes willbe small even over a period of several months. If grainsare stored with a higher than ideal moisture content,grain and microbial amylases may begin to breakdownthe starch, leading to a deterioration of grain quality(Macrae

et al

. 1993). Unsaturated acids can be oxidisedto produce off-flavours and rancid odours (Macrae

et al

.1993). There is little change in protein content, andJood & Kapoor (1994) found little change in the vita-min content of wheat, maize and sorghum grains duringstorage (up to 4 months) in insect-free conditions. Ricemay be aged for 3–4 months to improve the millingyield and to make the milled rice expand more duringcooking (Macrae

et al

. 1993).

2.3 Processing

Cereals typically undergo a range of processes to pro-duce a variety of different products, including non-foodproducts. Milling is the main process associated withcereals, especially the bread cereals wheat and rye.Slightly different milling techniques are used for the var-ious cereals (see below) and a range of other processesmay also be used (

e.g.

extrusion and fermentation) inthe production of cereal products. As well as havingtechnical consequences, processing also changes thenutritional content of cereals.

2.3.1 Milling

The process of milling can basically be described asgrinding, sifting, separation and regrinding. These stepsare repeated to extract a particular part of the grain, theendosperm. Before milling begins, the cereal grains arecleaned. Most modern equipment uses differences insize, shape, colour, solubility, specific weight andresponse to magnetic force to separate foreign materialfrom the grains. Prior to grinding, water may be addedto the cereal, which is allowed to rest before milling(

tempering

). This allows absorption of water by thegrains, toughening the pericarp and germ so they do notsplinter during milling. If heat is also applied duringtempering (to mellow the endosperm and make it easierto grind), then the process is referred to as

conditioning

(Hoseney 1994). To ensure production of a uniformproduct, different grains may be blended prior to millingand this is referred to as

gristing

(Fig. 4).

Table 3

Codex standards for maximum moisture content (%) of selected cereals

Grain

Maximummoisturecontent* Codex Alimentarius Standard†

Maize 15.5% Codex Standard 153-1995Oats 14.0% Codex Standard 201-1995Rice 15.5% Codex Standard 198-1995Sorghum 14.5% Codex Standard 172-1989a

(Revision 1-1995)Wheat 14.5% Codex Standard 199-1995Durum wheat 14.5%Whole and decorticated

pearl millet grains13.0% Codex Standard 169-1989b

(Revision 1-1995)

*Lower moisture limits required for certain destinations in relation to climate,duration of transport and storage.

†

Codex Alimentarius 1989a, 1989b,1995a, 1995b, 1995c, 1995d.


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Figure 4 General stages of milling (reproduced with kind permission of National Association of British & Irish Millers (NABIM)).

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© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111–142

In ancient times, milling was performed using stonesto crush the grain. Now grains are ground between tworotating rollers. The first grinding stage through agroove (referred to as breaking) opens the kernel andscrapes off the endosperm. Then smooth ‘sizing’ and‘reduction’ rollers decrease the endosperm granules to afine flour. After each stage of grinding, material is sent toa sifting machine, where rotating sieves with differentlysized apertures separate particles of similar size. Theseparticles are then purified using air currents to separateout endosperm and bran.

Milling rye Although this is similar to milling wheat, ryeis more prone to ergot (see section 2.4) so great care istaken to remove this fungus during cleaning. Rye is alsotempered for a shorter period of time (6 h) because ryekernels are softer than wheat kernels (Hoseney 1994).

Milling sorghum and millets These cereals are mainlyprocessed by traditional methods, using a hand-operated wooden pestle and mortar. Generally thegrains are pounded and the husk removed by winnow-ing or floatation. The grains are pounded further beforesieving (to remove coarse material which is poundedagain) to produce flour and meal.

Milling rice Whole (paddy) rice is dehulled by a rubber-roll sheller to produce brown rice and coarse bran (fromthe husk). Brown rice can be further processed toremove the bran and produce white rice by pearling orwhitening, and polishing (Hoseney 1994).

Milling barley Barley is shelled and the husk removed(via aspiration) before sifting and cutting. Barley maythen be pearled, with extensive pearling (removal ofover 50% of the original grain) producing pearl barleyand as a by-product, barley flour (Kent & Evers 1994).

Milling oats Two different systems have developed: thetraditional or dry-shelling system and the modern green-shelling system. As can be seen from Table 4, they shareseveral similar steps (Kent & Evers 1994).

Milling corn Corn may be dry or wet milled. After tem-pering, dry milling uses a degerminator (two cone-shaped surfaces, one rotating inside the other) to removethe hull and break the germ free from corn kernels. Theendosperm is then reduced to grits using roller milling,similar to that used for wheat (Hoseney 1994). From thisa number of products are manufactured such as hominyand polenta, the Italian porridge. Wet milling separatescorn into its four basic components – starch, germ, fibreand protein. After steeping for 30–40 h, the next step in

the process involves a coarse grind to separate the germfrom the rest of the kernel. The remaining slurry is finelyground and screened to separate the fibre from the starchand protein. The starch is then separated from theremaining slurry. The starch can then be converted tosyrup, or it can be made into several other productsincluding paper, paints, ethanol and laundry detergents.

2.3.2 Technical consequences of milling

During milling, several technological changes occur.Firstly, there may be mechanical changes to the starch,which can increase the level of enzyme activity. Thesechanges are important in bread making to provideaccess for the alpha-amylase to work and so are notintrinsically negative. The extent of this change willdepend on the quality of the grain and the parameters ofmilling. Generally, the harder the grain, the greater theextent of changes.

Secondly, there may be changes to the proteins withinthe grains. During grinding, temperatures may reach50–60∞C, which can denature the cereal’s proteins. Thiscan lead to a lower wet gluten yield, which decreases thewater absorption capacity of the flour. To prevent this,excessive heating of the milled material is avoided.

After milling, flour is stored or aged. If this occursunder normal atmospheric conditions, normal temper-ature and normal humidity, it can beneficially affect thequality of the flour. During ageing the flour will changein colour from cream to white and it will develop betterbaking properties (the gluten quality improves and itsextensibility decreases). Although ageing of wheat flourmay last up to 6 weeks, the major changes take placewithin the first 10–12 days after milling. Rye flour agesfaster and so is aged for a shorter time (only about2 weeks). Upon storage, rice undergoes ‘after-ripening’,a series of biochemical changes which can influenceproperties such as cooking time and stickiness (Kent &Evers 1994).

Table 4 Methods used to mill oats

Modern method Traditional method

Width grading

Shelling (by impact) Stabilisation (inactivation of enzymes)Stabilisation Kiln dryingKiln drying Length gradingLength grading Shelling (on stones)

Cutting

Grinding (for oatmeal, oat flour and bran)Steaming and flaking (for rolled oats)

Nutritional aspects of cereals 121


During milling there are risks of contamination frommetallic fragments, mineral dust (e.g. sand), pests,microorganisms and heavy metals. However, controlsset nationally and internationally limit the extent towhich these contaminants can enter the food chain.

2.3.3 Nutritional consequences of milling

Fractionation of the grain during milling rather than themilling process per se, is important from a nutrition per-spective. As fibre, vitamins and minerals tend to be con-centrated in the outer bran and aleurone layers of thegrain, the final nutrient content will depend on theextent to which these layers are removed during pro-cessing (MacEvilly 2003). Generally, the more processedthe grain, the lower the proportion of vitamins in thefinal flour (Ottaway 1999). For example, white flourmay have less than one-third of the mineral and vitamincontent of wholegrains, although vitamins and mineralsare often added back after milling (see section 4.1). Mill-ing may decrease some of the bioactive substances (phy-tochemicals) that are found in cereals. For example,Liukkonen et al. (2003) found the content of severalphytochemicals (e.g. lignans and phenolic acids)decreased after milling. For more information on phy-tochemicals, see section 3.2.4.

Starch and protein are less affected by processing asthese nutrients are concentrated in the endosperm of thegrain (Goldberg 2003). Milling, decortication, fermen-tation and germination will increase protein digestibility(due to the removal of fibre and enzymic breakdown ofproteins) but milling and decortication reduce the levelof lysine, the limiting amino acid in cereals (Macraeet al. 1993). Refined grains also have a higher glycaemicindex (GI) than wholegrain products (Ludwig & Eckel2002; see section 3.4 for more on GI). Some of thegrain’s lipids, which are mainly present in the germ andbran, are distributed during milling into other fractions(Southgate 1993).

2.3.4 Other processes

As well as milling, a range of other processes are used inthe production of cereals and cereal products. Generally,the techniques used result in fragmentation of the foodmatrix and gelatinisation of the starch granules. Thismakes them readily digestible and generally they havehigher GI values. Cereal protein may be damaged duringsome of the processes used to produce cereal products –e.g. baking can lead to lysine loss (Southgate & Johnson1993). Antioxidant activity (which is relatively high inwholegrain cereal products) can be increased by brown-

ing reactions such as baking and toasting processes andmay be due to the formation of intermediate substancesfrom Maillard reactions with antioxidant activity(Slavin 2003).

Many cereal-based foods undergo processing involv-ing heat. This may affect the bioavailability of mineralssuch as iron, calcium and zinc, e.g. availability may beimproved because of the hydrolysis of phytates byphytase enzymes. Processes involving boiling may leadto losses of around 40% for most B vitamins, althoughlosses of folate will be slightly higher. Losses during bak-ing are generally lower, except for folate (MacEvilly2003).

Recently, work in Sweden found baking starchy foodssuch as rice and cereals could lead to the formation of asubstance called acrylamide. Acrylamide, which hasbeen described as a ‘probable carcinogen’, has beenfound in a range of foods, including crisps, potato chipsand cereal products. No link between acrylamide levelsin food and cancer risk has been established and basedon the evidence to date, the UK Food Standards Agencyhas advised the public not to change their diet or cook-ing methods (Kelly 2003). However, the EU’s ScientificCommittee on Food has endorsed recommendationsmade by Food and Agriculture Organisation (FAO)/World Health Organization (WHO) in 2002 whichinclude researching the possibility of reducing levels ofacrylamide in food by changes in formulation and pro-cessing (see http://europa.eu.int/comm/food/fs/sc/scf/out131_en.pdf for more details).

Parboiling Rice is soaked in warm water (65∞C) for 4–5 h before being steamed under pressure, dried andmilled. This process increases the total and head yield ofthe rice and decreases the loss of nutrients during pro-cessing (see below). Polishing rice removes the bran lay-ers and the germ, leading to substantial losses in Bvitamins and a decrease in energy content [although theenergy available is higher in milled rice because it con-tains less non-starch polysaccharides (NSP) on a weightfor weight basis]. Before polishing, unhusked rice maybe parboiled (steamed or boiled after soaking) to softenthe husk. During this process, some of the water-solubleB vitamins located in the bran move into the endosperm,along with some of the oil. Although cooking and par-boiling rice reduces its protein digestibility by 10–15%,there is a corresponding increase in the biological value,leading to an unchanged net protein utilisation value(Table 5).

Alkali processing The traditional method used to pro-duce corn tortillas mixes maize with water and lime (cal-

http://europa.eu.int/comm/food/fs/sc/scf/

122 Brigid McKevith


cium hydroxide). After cooking, the mixture is steepedovernight before being washed with fresh water toremove the loosened pericarp and any residual alkali(Macrae et al. 1993).

Fermentation Fermentation is used to produce a num-ber of cereal products including bread, and alcoholicbeverages such as beer, vodka and whiskey. Examples offermented cereal foods include kenkey, made from a fer-mented maize dough in Ghana and tapé ketan, a ricedessert in Indonesia (Macrae et al. 1993). During breadmaking, fermentation produces carbon dioxide makingthe dough rise and increasing its volume. During theproving stage, mechanically damaged starch grains arebroken down by amylase to produce maltose, which isimportant for maintaining yeast activity (and thereforegas production). In addition to yeast, lactic acid bacteriaare used in the production of sourdough bread to pro-vide an acidic flavour to the final product. Some of thebioactive substances in rye increase in sourdough bak-ing (Liukkonen et al. 2003). The bacteria also affect thedough proteins, making the dough stronger. In alcoholproduction, fermentation produces ethanol and carbondioxide. In other fermented cereal products, the bio-availability of minerals may be higher than in similarnon-fermented products due to the partial breakdownof the phytate. Fermentation may also improve proteinquality because of bacterially produced lysine and byimproving protein digestibility (Macrae et al. 1993).

Extrusion The extrusion process uses a screw press witha restricted opening to produce a shaped food product.Extrusion cooking uses this process in addition to heat(a high-temperature short-time procedure) to manufac-ture a range of food products, including breakfast cereals

and pasta. Gualberto et al. (1997) found extrusion hadno effect on the insoluble fibre content of wheat bran butobserved decreased amounts in rice and oat brans. Theamount of soluble fibre increased in all three brans afterextrusion, except at the maximum screw speed (100%maximum rotations per minute). The phytate content ofthe three cereal brans was not affected by extrusion.Sandberg et al. (1986) found that extrusion cookingcould impair the digestion of phytate in a high-fibrecereal product owing to loss of phytase activity. Noeffect was seen in absorption of iron and calcium but asmall decrease in the absorption of zinc, magnesium andphosphorus led the authors to suggest that this couldhave implications for foodstuffs consumed frequently(Kivisto et al. 1986). In a more recent study, Fair-weather-Tait et al. (1989) found extrusion cooking hadno effect on the retention of iron or zinc in adults.

Other processes In the production of breakfast cereals,a number of other processes may be used (Fast & Cald-well 2000). For example, flaked cereals can be madefrom wholegrains or parts of the wholegrain or fromfiner flour materials, with great pressures being used toflatten the prepared material into flakes. Puffed cerealsare produced using either puffing guns (which are capa-ble of holding very high temperature and high-pressuresteam) or an oven. Shredded cereals are produced bypassing the tempered grain between two rollers, one ofwhich is grooved and the other smooth. The grain issqueezed into the grooves of the roller and emerges asstrands which are removed, accumulated in layers andformed into biscuits or bite-sized pieces.

2.4 Cereals and food safety

Damage to cereals can occur in the field as well as afterharvesting. In addition to problems with pests, mouldsand fungi can contaminate cereals.

2.4.1 Pests

Infestation of cereal crops by pests can be a problem,both before and after harvest. Insects (e.g. mites andweevils) cause the most damage in stored cereals. Insectscan produce substances with unpleasant tastes andsmells (such as uric acid) and some transmit pathogenicbacteria. They can also affect the cereal’s nutritionalvalue, for example, decrease the carbohydrate contentand increase free fatty acid levels (Chelowski 1991).Jood & Kapoor (1994) found insects could affect thevitamin content of cereals, decreasing the thiamin con-tent by up to 69%, riboflavin content by up to 67% and

Table 5 Comparison of selected nutrients in brown rice and white rice (per 100 g)

Nutrient Brown rice, raw White rice (easy cook), raw

Energy (kcal/kJ) 357/1518 383/1630Fat (g) 2.8 3.6Protein (g) 6.7 7.3Fibre (as NSP) (g) 1.9 0.4Thiamin (mg) 0.59 0.41Riboflavin (mg) 0.07 0.02Niacin equivalents (mg) 6.8 5.8Folate (mg) 49 20

NSP, non-starch polysaccharides.Source: Food Standards Agency and Institute of Food Research 2002.© Crown copyright material is reproduced with the permission of theController of HMSO and Queen’s Printer for Scotland



niacin by up to 32%. When infestations are detected ina silo or a ship, insecticides may be used, although thetype of insecticide and the level used are tightly con-trolled (Macrae et al. 1993). Birds and rodents can alsocontaminate stored cereals and cause food safety prob-lems (Appert 1987).

2.4.2 Other contaminants

There is potential for contamination of cereals andcereal products at many different stages, e.g. duringgrowth, harvest and storage. Mycotoxins are toxicchemical substances produced by certain forms ofmould under specific conditions. A number of mouldsproduce toxins (see Table 6). The most important myc-otoxin with respect to cereals is produced by Aspergillusflavus (Macrae et al. 1993). As mycotoxins are naturalcontaminants of cereals, it is normal for small quantitiesto appear in harvested cereals. Mycotoxins are only athreat to human health if they are absorbed in largequantities. A range of preventative strategies are used toprevent the formation of mycotoxins before and afterharvest. Although mycotoxins are relatively stable, cer-tain manufacturing processes can reduce their level, e.g.milling of white flour removes deoxynivalenol which isconcentrated in the external layers of the bran (Quillien2002).

Ergot is a fungus that can be found on a large numberof plants around the world (Lorenz 1979). Clavicepspurpurea, the ergot of medical importance, grows onrye. Consumption of infected rye is harmful and canlead to ergotism (also called Saint Anthony’s fire),which produces gangrenous necrosis and hallucinations(Macrae et al. 1993; Bender & Bender 1999). Ergotrarely enters commercial food channels because of strictgrain standards but ergotism still occurs in animals fromtime to time (Lorenz 1979).

Other problems that occur in cereals include rusts (afungal disease caused by species of Puccinia) and smutdiseases, which are caused by fungi which producemasses of soot-like spores on the leaves, grains or ears.

2.5 Key points

• Wheat is the largest cultivated cereal crop, accountingfor 30% of the world’s cereal production. Rice is thesecond most important crop on a world basis, account-ing for 21% of the world’s cereal production.• Post-harvest, good grain storage is important to min-imise losses, with moisture content a key factor.• Cereals undergo a range of processing, the mostcommon being milling, which affect their technologicaland nutritional properties. Generally, the final nutrientcontent of a cereal will depend on the extent to whichthe outer bran and aleurone layers are removed dur-ing processing, as this is where the fibre, vitamins andminerals tend to be concentrated. Recently, acryla-mide has been found in starchy baked foods. No linkbetween acrylamide levels in food and cancer risk hasbeen established and based on the evidence to date, theUK Food Standards Agency has advised the public notto change their diet or cooking methods (Kelly 2003).However, the EU’s Scientific Committee on Food hasendorsed recommendations made by FAO/WHOwhich include researching the possibility of reducinglevels of acrylamide in food by changes in formulationand processing.• There is potential for contamination of cereals andcereal products by pests, mycotoxins, rusts and smuts.

3 The role of cereals in health and disease

Cereals have a long history of use by humans, datingback to prehistoric times. Cereals are staple foods, withcurrent estimates of annual cereal consumption at166 kg per capita in developing countries and 133 kg indeveloped countries (FAO 2003). Cereals provide arange of macro- and micronutrients and a high con-sumption of cereals has been associated with adecreased risk of developing several chronic diseases.

3.1 History of cereals in the diet

There is evidence to suggest that wild cereals were eatenby human hunter-gatherers in ancient times (Toussaint-Samat 1994). For example, sorghum has been used sinceprehistoric times in Africa, Asia and Europe and prob-ably originated in North Africa around 3000 BC (Kent& Evers 1994). The origin of rice may be traced to aplant grown in India at the same time, but it is first men-tioned historically in China in 2800 BC. This is roughlythe same time maize was being grown in America. Whilewild barley and wheat were grown in parts of the Mid-dle East around 10 000 BC, these varieties producedlow yields because they were brittle and shed their seeds.

Table 6 Examples of moulds producing mycotoxins in cereals

Mould Mycotoxin produced

Aspergillus flavus Aflatoxins B1 and B2Penicillium verrucosum (temperate regions) OchratoxinAspergillus ochraceus (tropical regions)Fusarium species Fumonisins

ZearlenoneDeoxynivalenol

124 Brigid McKevith


Due to natural mutations, more sturdy varieties devel-oped and these were selected for cultivation and cerealcrops spread, reaching Britain sometime between 4000and 2000 BC (Vaughan & Geissler 1997). Rye wasdomesticated in Germany at about the same time (Kent& Evers 1994).

Cereals were obviously an important part of ourancestors’ lives, as cereals appear in a number of mythsand legends. For example, barley and wheat wereviewed as gifts from one of the gods, while the Aztecsbelieved the same for corn (Toussaint-Samat 1994;Werner 1997). Cereals play a pivotal role in a number ofdifferent religions, including rice in the Japanese religionof Shinto and bread in Christianity.

3.2 Nutritional value of cereals

Cereals are staple foods, providing a major source ofcarbohydrate, protein, B vitamins and minerals for theworld’s population. As well as containing a range ofphytochemicals which may provide some of the healthbenefits seen among populations consuming diets basedon plant foods (see Goldberg 2003), cereals also containa number of anti-nutrients.

3.2.1 Macronutrients

Carbohydrate Cereals are often classed as carbohy-drate-rich foods, as they are composed of approximately75% carbohydrate. Starches, the major component ofthe cereal, occur in starch granules in the endosperm.Starch granules differ in size (e.g. in rice they have adiameter of only 5 mm, while in wheat they may be 25–40 mm) and shape (either large, lens-shaped granules or

small, spherical granules). The ratio of amylose to amy-lopectin within the starch granules varies, depending onthe cereal and its variety. Within common varieties ofcereals, 25–27% of starch is present as amylose, while inwaxy varieties (e.g. rice and corn) most of the starch isamylopectin (see Fig. 5). However, in cereal products, aproportion of this starch is not digested and absorbed inthe small intestine. This is referred to as resistant starchand it appears to act in a similar way to dietary fibre.Four categories of resistance have been defined(Baghurst et al. 1996):

• RS1 refers to starch that is physically inaccessible fordigestion as it is ‘trapped’ (e.g. intact wholegrains andpartially milled grains).• RS2 refers to native resistance starch granules (e.g.found in high amylose maize starch).• RS3 refers to retrograded starch (e.g. found in cookedand cooled potatoes, bread and some types of corn-flakes).• RS4 refers to chemically modified starch (e.g. com-mercially manufactured starches).

A small amount of free sugars is also present (~1–2%),mainly as sucrose but low concentrations of maltose andvery low concentrations of fructose and glucose occur.

Protein Cereals contain about 6–15% protein (Gold-berg 2003). The major storage proteins in wheat are gli-adins and glutenins, while in rice it is glutelin (oryzenin),in maize it is prolamin (zein); barley has hordeins andglutelins, and in oats there are albumins and globulins(Kulp & Ponte 2000). Although cereals provide a goodrange of amino acids, the building blocks of proteins,some are present in relatively low amounts. Essentialamino acids must be supplied by the diet, and from these

Figure 5 Approximate amylose and amylopectin content of selected cereals.

0

25

50

75

100

Stand

ard

maiz

e

Wax

y maiz

e

High a

mylo

se m

aize

Rice

Whe

at

Cereal

Ap

pro

xim

ate

con

ten

t o

f st

arch

es (

%)

Amylose

Amylopectin



the human body is able to make other (termed non-essential) amino acids for itself (Table 7). The essentialamino acid that is in shortest supply in relation to needis termed the limiting amino acid. For cereals the limit-ing amino acid is lysine, except for rye, where tryp-tophan is the first limiting amino acid (Macrae et al.1993). More favourable essential amino acid composi-tions can be found in rice, rye, barley and high-lysinecultivars (e.g. maize, sorghum and barley) (Macrae et al.1993). Combining cereals with other plant foods (e.g.rice and beans) can compensate for these limiting aminoacids.

Lipids Although the germ is the richest source of lipids,overall, lipids are only a minor component of cereals,with the amount varying from a lipid content of 1–3%in barley, rice, rye and wheat, to 5–9% in corn and5–10% in oats, on a dry-matter basis (Southgate 1993).This lipid fraction is rich in the essential fatty acidlinoleic acid (C18:2) (Table 8).

3.2.2 Micronutrients

Cereals can contribute to vitamin and mineral intake,although the micronutrient content will depend on theproportion of germ, bran and endosperm present (seesection 2.3). The pericarp, germ and aleurone layer arerich in vitamins and minerals so refined cereal productslose some of these nutrients, although in the UKlegislation requires the addition of thiamin, niacin,calcium and iron to wheat flour (except wholemeal).Such legislation currently varies between countries inthe EU.

Vitamins Cereals contain no vitamin C or vitamin B12,no vitamin A and, apart from yellow corn, no beta-carotene (Courdain 1999). However, cereals are animportant source of most B vitamins, especially thia-min, riboflavin and niacin (Kulp & Ponte 2000). Cere-als also contain appreciable amounts of vitamin E(Table 9).

Table 7 Essential amino acid composition of cereal grains

Amino acid(g/ 100 g protein)

Wheat(hard)

Rice Maize Barley Oats RyeMillet(average of 7 types)

Sorghum

B M N HL N HL

Phenylalanine 4.6 5.2 5.2 4.8 4.3 5.2 5.4 5.0 5.5 5.1 4.9Histidine 2.0 2.5 2.5 2.9 3.8 2.1 2.4 2.4 2.0 2.1 2.3Isoleucine 3.0 4.1 4.5 3.6 3.4 3.6 4.2 3.7 3.8 4.1 3.9Leucine 6.3 8.6 8.1 12.4 9.0 6.6 7.5 6.4 10.9 14.2 12.3Lysine 2.3 4.1 3.9 2.7 4.3 3.5 4.2 3.5 2.7 2.1 3.0Methionine 1.2 2.4 1.7 1.9 2.1 2.2 2.3 1.6 2.5 1.0 1.6Threonine 2.4 4.0 3.7 3.9 3.9 3.2 3.3 3.1 3.7 3.3 3.3Tryptophan 2.4 1.4 1.3 0.5 0.9 1.5 - 0.8 1.3 1.0 0.9Valine 3.6 5.8 6.7 4.9 5.6 5.0 5.8 4.9 5.5 5.4 5.1

B, brown; M, milled; N, normal; HL, high-lysine.Source: Macrae et al. 1993.Reprinted from Encyclopaedia of Food Science, Volume 2, Serna-Saldivar. ‘Dietary importance (cereals)’, p. 787, © 1993, with permission from Elsevier.

Table 8 Fatty acid profiles of selected cereals

Fat & fatty acids(g/100 g food) Barley, pearl, raw

Oatmeal,quick cook, raw Wheat flour, white Rye flour Rice, brown, raw Rice, white, raw

Total fat 1.7 9.2 1.2 2.0 2.8 3.6Saturated fatty acids 0.29 1.61 0.16 0.27 0.74 0.85Cis-monounsaturated fatty acids 0.14 3.34 0.13 0.21 0.66 0.91

Polyunsaturated fatty acids:Total cis 0.77 3.71 0.51 0.95 0.98 1.29n-6 (as 18:2) 0.70 3.52 0.48 0.82 0.94 1.26n-3 0.07 0.19 0.03 0.13 0.04 0.03

Source: Ministry of Agriculture, Fisheries and Food 1998.© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland

126 Brigid McKevith


Minerals Cereals are low in sodium and are a goodsource of potassium, in common with most plant foods.Wholegrain cereals also contain considerable amountsof iron, magnesium and zinc, as well as lower levels ofmany trace elements, e.g. selenium. Rice contains thehighest level of selenium among the cereal grains, pro-viding between 10 and 13 mg per 100 g (Table 10). Theselenium content of a cereal will vary depending on theselenium content of the soil; for example, the seleniumcontent of wheat-grain can range from 0.001 mg per100 g to 30 mg per 100 g (Lyons et al. 2003). Wheatgrown in North America generally has a higher sele-nium content compared to that grown in Europe andthe switch to European wheat in recent years is sug-gested as the main explanation of falling seleniumintake in the UK, although the effect (if any) of thisdecrease on health is not currently known (Goldberg2003).

3.2.3 Non-starch polysaccharides

All cereals are a rich source of NSP. There are two typesof NSP – insoluble and soluble – and, although bothmay help with weight control (by delaying food leavingthe stomach), they have different effects in the body (seesection 3.3). The insoluble NSP content of most cerealsis similar, while the composition of the water-solubleNSP varies. Arabinoxylans are the main water-solubleNSP in wheat, rye and barley, while in oats it is the beta-glucans. The amounts of beta-glucans and arabinoxy-lans are higher in barley, oats and rye compared towheat (on a dry weight basis, 3–11%, 3–7%, 1–2% and<1%, respectively) (Wood 1997).

3.2.4 Phytochemicals

Cereals contain a range of substances, which may havehealth-promoting effects, that are often referred to as

Table 9 Vitamin content of selected cereals (mg/per 100 g, unless specified)

Vitamin Vitamin E Thiamin Riboflavin Niacin equivalent (mg) Vitamin B6 (mg) Folate (mg)

Wheat flour, white, plain 0.30 0.31† 0.03 3.6† 0.15 22Wheat flour, wholemeal 1.40 0.47 0.09 8.20 0.50 57Rice, easy cook white, raw (0.10) 0.41 0.02 5.8 0.31 20Rice, brown, raw 0.80 0.59 0.07 6.80 N 49Popcorn, plain 11.03 0.18 0.11 1.7 0.20 3Oatmeal, quick cook raw 1.50 0.90 0.09 3.4 0.33 60Barley, pearl raw* 0.40 0.12 0.05 4.8 0.22 20Rye flour, whole 1.60 0.40 0.22 2.6 0.35 78Millet flour* Trace 0.68 0.19 2.8 N N

*From Holland et al. 1988. †These values are for fortified flour.N, the nutrient is present in significant quantities but there is no reliable information on the amount; (), estimated value.Source: Food Standards Agency and Institute of Food Research 2002.© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland

Table 10 Mineral content of selected cereals (mg/per 100 g, unless specified)

Mineral Na (mg) K (mg) Ca (mg) Mg (mg) Fe (mg) Zn (mg) Se (mg)

Wheat flour, white, plain 3 150 140† 20 2.0† 0.6 2Wheat flour, wholemeal 3 340 38 120 3.9 2.9 6Rice, easy cook white, raw 4 150 51 32 0.5 1.8 13Rice, brown, raw 3 250 10 110 1.4 1.8 10Popcorn, plain 4 220 10 81 1.1 1.7 NOatmeal, quick cook raw 9 350 52 110 3.8 3.3 3Barley, pearl raw* 3 270 20 65 3.0 2.1 (1)Rye flour, whole (1) 410 32 92 2.7 3.0 NMillet flour* 21 370 40 N N N N

*From Holland et al. 1988. †These values are for fortified flour.N, the nutrient is present in significant quantities but there is no reliable information on the amount; ( ), estimated value.Source: Food Standards Agency and Institute of Food Research 2002.© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland



phytochemicals or plant bioactive substances (see Gold-berg 2003). Although flavonoids are only present incereals in small quantities, a number of other antioxi-dants are present, including small amounts of tocot-rienols, tocopherols and carotenoids. In laboratorystudies, wholegrain breakfast cereals have been found tohave an antioxidant content similar to fruits and vege-tables (Miller et al. 2000) and one study suggests thatthe major contributors of overall antioxidant activityare bound phytochemicals (Adom & Li 2002). Lignansare a type of phytoestrogen found in cereals, andalthough the amount may be low (e.g. compared to thatin linseed), cereals may be an important source becauseof the large quantities eaten daily.

3.2.5 Anti-nutrients

As previously mentioned, cereals contain relatively highlevels of phytate. On a dry weight basis, corn contains0.89% phytate, soft wheat 1.13%, brown rice 0.89%,barley 0.99% and oats 0.77% (Cheryan 1980). In mostcereals, the phytate is concentrated in the aleurone layerand, to a lesser extent, the germ (Làsztity & Làsztity1990). This means that milling affects the level ofphytate of most cereals, e.g. white flour has almost nophytate remaining (Anon 1979). Phytate can bind min-erals such as iron, calcium and zinc, and there is someevidence showing decreased absorption of these miner-als in the presence of phytate (e.g. McCance andWiddowson observed a decreased absorption of calciumin humans when phytate was added to white bread)(Harris 1955). The extent to which this affects nutrientstatus will depend on a number of factors, including theamount of phytate hydrolysed during processing or theamount that is digested in the gut; the concentration ofphytate and minerals in the food and the overall diet andthe nutrient status of the individual. This effect may beof particular relevance to those people consuming a low-calorie diet (Làsztity & Làsztity 1990).

Tannins, which are found for example in brown sor-ghum, can bind and precipitate protein, decreasing itsdigestibility. Germination and treatment of sorghumwith calcium oxide, potassium carbonate, ammoniumbicarbonate or sodium bicarbonate improves the nutri-tional value of the grain. Pearl millet barley contains agoitrogen (thioamide), found in the bran andendosperm. Trypsin inhibitors, which can impair pro-tein digestability, have also been isolated in pearl milletand rye, although these are normally deactivated byheating (Bender & Bender 1999). Rye also containsother anti-nutrients, which have an impact in animalnutrition but are of little concern to humans as they are

either removed during processing or destroyed duringbaking.

3.3 Contribution of cereals and cereal products in the diet

Cereal products play a central role in most countries andare staple foods for much of the world’s population. Inthe UK’s Balance of Good Health food model, cerealsand cereal products are grouped with bread and pota-toes and this group of foods should form a main part ofmeals (Fig. 6). The dietary guidelines accompanying theBalance of Good Health encourage ‘plenty of foods richin starch and fibre’. Many of the foods in this groupcould be described as wholegrain foods, although nolegal definition currently exists in the UK (although theAmerican definition of a minimum of 51% wholegrainingredient has been used by the Joint Health Claims Ini-tiative). Currently America is the only nation to makespecific recommendations regarding wholegrain foods(three servings a day) (Lang & Jebb 2003).

Table 11 shows the contribution that cereals andcereal products (including bread, pasta, breakfast cere-als, biscuits, cakes and pastries) make to the UK diet.Cereals and cereal products are an important source of

Table 11 Average contribution of cereals and cereal products to the nutrient intake in the UK

Nutrient

% contribution of cereals to average intake of nutrients

Boys* Girls* Adults†

Energy 35 33 31Protein 27 26 23Carbohydrate 45 42 45Fat 22 21 19Fibre (as NSP) 40 37 42Thiamin 43 38 34Riboflavin 34 31 24Niacin 38 34 27Folate 44 37 33Vitamin B6 30 26 21Vitamin D 37 35 21Iron 55 51 44Calcium 27 27 30Sodium 40 38 35Potassium 15 14 12

NSP, non-starch polysaccharides.*Children National Diet and Nutrition Survey (NDNS) from Gregory et al.2000. †Adult NDNS data from Henderson et al. 2003a, 2003b.© Crown copyright material is reproduced with the permission of theController of HMSO and Queen’s Printer for Scotland

128 Brigid McKevith


magnesium (providing 27% of the average adultintake) and zinc (providing 25% of the average adultintake) (Henderson et al. 2003b). It is also estimatedthat about one-fifth of the UK’s selenium intake is fromcereals and cereal products (Goldberg 2003). Cerealproducts also contribute a considerable proportion ofsodium, mainly from bread (15%, 14% and 14% forboys, girls and adults, respectively). Although cerealsare naturally low in sodium, during production ofcereal products sodium is added. If manufacturers con-tinue to reduce the sodium content of cereal products itwill help the population to reduce average total sodiumintake.

As can be seen from Table 11, cereals and cerealproducts play an important role in the diet and are themain source of many nutrients for both children andadults. This is in part due to the mandatory fortifica-tion of all wheat flour (apart from wholemeal) withiron, calcium, thiamin and niacin, and the voluntaryfortification of breakfast cereals. This is demonstratedby the 20% contribution fortified breakfast cerealsmake to the average intake of iron in the UK adultpopulation.

3.3.1 Bread

Bread making goes back to prehistoric times, when amixture of grass seeds was ground into a crude form offlour, to which water was added to form a dough(Patient & Ainsworth 1994). Bread is made from fouringredients – flour, water, yeast and salt and in the UKmost bread is produced using wheat flour, althoughother flours, e.g. rye, are sometimes used. Differenttypes of bread are produced from wheat flour dependingon the proportion of the grain used, with brown breadsbeing made from flour of an intermediate extraction rate(about 80–85%).

The traditional method of bread making involves themixing of the four ingredients to form a dough, which isthen kneaded to develop the gluten, before being left tostand (during which time fermentation occurs). As thismethod is quite time-consuming and labour-intensive, amechanical method, the Chorleywood process, wasdeveloped which uses a mechanical mixer, a fast-actingdough improver and a small amount of fat (Kent &Evers 1994).

White bread may be the most commonly eaten food in

Figure 6 Balance of Good Health (British Nutrition Foundation version).



the UK; data from the recent adult National Diet andNutrition Survey (NDNS) indicated that 93% of menand 89% of women ate it during the 7-day recordingperiod (Henderson et al. 2002). In the UK, weeklyhousehold consumption of bread has decreased byalmost 1 kg since the 1940s. However, over the last10 years there has been an increase in breads such asFrench bread, naan bread, pitta bread and bagels(DEFRA & National Statistics 2001). The current aver-age adult intake of bread (including wholemeal, softgrain and other bread) is about 91 g a day, roughly threeslices (Henderson et al. 2002).

The typical nutrient content of different breads isgiven in Table 12. In terms of macronutrients, about40% of bread is carbohydrate and 8–9% is protein; thebreads are all low in fat (less than 3 g of fat/100 g).However, the fibre content is significantly higher inwholemeal and brown bread than white bread.

3.3.2 Breakfast cereals

Developed in the late 19th century in America andintroduced to the UK in the early 20th century, RTEbreakfast cereals are an important source of nutrients.For example, in a sample of schoolchildren in North-ern Ireland, fortified RTE breakfast cereals were asso-ciated with higher daily intakes of most micronutrientsand fibre, and with a macronutrient profile consistentwith current nutritional recommendations. Inadequateintakes of riboflavin, niacin, folate and vitamin B12

(and iron in girls) were more likely in those childrennot consuming fortified breakfast cereals (McNulty

et al. 1996). Although vitamin D is not usually associ-ated with breakfast cereals, because of fortification ofRTE breakfast cereals, the recent NDNS report indi-cated that they now account for 13% of the averagedaily vitamin D intake in UK men and women (Hend-erson et al. 2003b) (Fig. 7). Similarly, in children,breakfast cereals account for 20% of the average dailyvitamin D intake in girls and 24% in boys (Gregoryet al. 2000).

Some recent work in schoolchildren has suggestedthat breakfast cereals may help maintain mental per-formance over the morning compared to no breakfastor a glucose drink (Wesnes et al. 2003). A small studyin adults also found that a high-fibre carbohydrate-rich breakfast was associated with the highest post-breakfast alertness rating and the greatest alertnessbetween breakfast and lunch (Holt et al. 1999). Alarger study found an association between breakfastcereal consumption and subjective reports of health,with those adults who ate breakfast cereal every dayreporting better mental and physical health, com-pared to those who consumed it less frequently (Smith1999).

3.3.3 Pasta

Pasta is traditionally made from very hard (durum)wheat, which is high in protein, and water. The mixtureis kneaded to produce a very stiff dough which is thenextruded, cut and dried. Pasta was bought to Britain inthe 18th century, and in 2000/2001 in Britain, amongthose men and women who ate pasta (52% men and53% of women), the mean consumption was 406 g and

Table 12 Typical nutrient composition per 100 g of bread

Nutrient White Brown Wholemeal

Energy (kcal/kJ) 219/931 207/882 217/922Protein (g) 7.9 7.9 9.4Carbohydrate (g) 46.1 42.1 42Total sugars (g) 3.4 3.4 2.8Starch (g) 42.7 38.7 39.3Fat (g) 1.6 2.0 2.5Fibre (as NSP) (g) 1.9 3.5 5.0Thiamin (mg) 0.24 0.22 0.25Niacin equivalents (mg) 3.6 4.9 6.1Folate (mg) 25 45 40Iron (mg) 1.6 2.2 2.4Calcium (mg) 177 186 106

NSP, non-starch polysaccharides.Source: Food Standards Agency and Institute of Food Research 2002.© Crown copyright material is reproduced with the permission of theController of HMSO and Queen’s Printer for Scotland

Figure 7 Contribution of breakfast cereals to the mean vitamin and mineral intake of UK adults (Henderson et al. 2003b).© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland

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130 Brigid McKevith


330 g a week, respectively (Henderson et al. 2002). Thenutrient content of white and wholemeal pasta is shownin Table 13.

3.3.4 Biscuits, buns, cakes and pastries

Although cereal foods are generally low in fat, this sub-group contributes 7% to the average daily intake oftotal fat in adults and 5% in children (Gregory et al.2000; Henderson et al. 2003a). Within the Balance ofGood Health, therefore, they do not fall into the samecategory as the cereal products discussed above. Biscuitsand buns, cakes and pastries form part of the group offoods containing fat; foods containing sugar.

3.3.5 Other foods containing cereals

Cereals and cereal products are used in a wide range ofother foods. Cereal-based porridges are traditionallyused as weaning foods in many parts of the world andwithin the UK baby cereals are often used at the firststage of weaning.

3.4 Cereals in health and disease

There is much interest in understanding the role of par-ticular foods, such as cereals, in the diet and their effecton health. Some of the work on cereals has focused spe-cifically on wholegrain cereals and work suggests thatpeople who eat wholegrains may have better nutrientintake profiles. For example, people in the USA who atewholegrains had higher intakes of vitamins and miner-als, and lower intakes of total fat, saturates and added

sugars compared to those who did not eat wholegrains(Cleaveland et al. 2000). Cereals may also have a rangeof health benefits as discussed below.

3.4.1 Energy balance

Cereal foods have a relatively low energy density, andfoods rich in wholegrain cereals may help reduce hungeras they are relatively bulky (Holt et al. 1999; Saltzmanet al. 2001). Cereals may also affect body weight regu-lation through effects on hormonal factors (Koh-Baner-jee & Rimm 2003). By focusing on increasing cerealintake, it is possible to achieve a reduction in consump-tion of other foods and a reduction in fat intake. Forexample, a small study using free-living subjects foundthat including 60 g of breakfast cereal with semi-skimmed milk every day decreased the average intake ofenergy from fat by 5.4%, with a similar increase inenergy contribution from carbohydrate (Kirk et al.1997). In another small study, 14 subjects consumedfour different breakfasts of the same energy content butwith differing macronutrient content – two fat-rich andtwo carbohydrate-rich (low or high fibre). The high-fibre, carbohydrate-rich breakfast was the most fillingmeal and was associated with less food intake during themorning and at lunch. Hunger returned at a slower rateafter this meal than after the low-fibre, carbohydrate-rich meal. Both fat-rich breakfasts were more palatablebut less satiating than the carbohydrate-rich meals (Holtet al. 1999). The recent WHO/FAO expert committeereport on nutrition and chronic diseases suggested that ahigh intake of NSP may be a protective factor againstoverweight and obesity (WHO/FAO 2003).

3.4.2 Glycaemic index (GI)

The GI is used for classifying carbohydrate-containingfoods. It can be defined as ‘the incremental area underthe blood glucose curve after consumption of 50 g car-bohydrate from a test food, divided by the area underthe curve after eating a similar amount of control food(generally white bread or glucose)’ (Ludwig & Eckel2002). The glycaemic load (GL) assesses the total gly-caemic effect of the diet and is the product of dietary GIand total amount of dietary carbohydrate (Jenkins et al.2002). The rate of digestion and absorption of carbo-hydrates is influenced by a range of factors (Pi-Sunyer2002), including:

• the nature of the monosaccharide components;• the nature of the starch (e.g. the amylose to amylopec-tin ratio);

Table 13 Nutrient content of white and wholemeal pasta (per 100 g)

Nutrient White (boiled) Wholemeal (boiled)

Energy (kcal/kJ) 104/442 113/485Protein (g) 3.6 4.7Carbohydrate (g) 22.2 23.2Total sugars (g) 0.5 1.3Starch (g) 21.7 21.9Fat (g) 0.7 0.9Fibre (as NSP) (g) 1.2 3.5Thiamin (mg) 0.01 0.02Niacin equivalents (mg) 1.2 2.3Iron (mg) 0.5 1.4Calcium (mg) 7 11

Source: Food Standards Agency and Institute of Food Research 2002.© Crown copyright material is reproduced with the permission of theController of HMSO and Queen’s Printer for Scotland



• cooking or food processing; (e.g. milling increases theGI of cereals);• other food components (e.g. fat, protein and fibre).

Several metabolic effects may be related to thereduced rate of glucose absorption after a low-GI food,e.g. a lower blood glucose concentration and a reducedpost-prandial rise in gut hormones and insulin, main-taining suppression of free fatty acids. The GI conceptsuggests a possible role for the rate of carbohydratedigestion in the prevention and treatment of chronic dis-ease. There may also be a role for low-GI foods inweight management, as they promote satiety. Althoughone study observed that a similar amount of weight lossoccurred with a high-GI diet as with a low-GI diet(Wolever et al. 1992), several intervention studies havefound that energy-restricted diets based on low-GI foodsproduce greater weight loss than those based on high-GIfoods (Brand-Miller et al. 2002). A systematic reviewhighlighted inconsistent results in short-term studiesmeasuring appetite sensations following low GI vs.high-GI foods. In terms of weight loss, the 20 longer-term intervention studies found no advantage in using alow-GI diet compared to a high-GI diet (1.5 kg loss ona low-GI diet vs. 1.6 kg on a high-GI diet) (Raben2002). Several epidemiological studies have also discov-ered a relationship between a high-GI diet and chronicdisease, e.g. coronary heart disease (CHD – see sectionon heart health), type 2 diabetes (see section on diabe-tes) and cancer (Jenkins et al. 2002).

A high-fibre wheat or high-fibre rye diet has beenshown to decrease post-prandial plasma insulin by 46–49% and post-prandial plasma glucose by 16–19% inoverweight, middle-aged men compared to a low-fibrediet but it is unclear if subjects were healthy, or hadimpaired glucose tolerance or type 2 diabetes (McIntoshet al. 2003). Although the authors suggested more com-prehensive testing should be undertaken, they concludedthat it was promising that even in the short term,wholegrain foods were capable of decreasing the glycae-mic response.

The recent WHO/FAO report on nutrition andchronic disease associated low-GI foods with an overallimprovement in glycaemic control in people with diabe-tes, and several countries educate people with diabetesabout GI. The WHO/FAO report also listed low-GIfoods as a possible factor in decreasing the risk of devel-oping type 2 diabetes and reducing the risk of weightgain (WHO/FAO 2003).

3.4.3 Heart health

Several large cohort studies in America, Finland andNorway have found that people eating relatively largeamounts of wholegrain cereals have significantly lowerrates of CHD and stroke. A recent review by Hu (2003)identified several prospective cohort studies showing aninverse association between wholegrain consumptionand risk of cardiovascular disease (CVD) (Table 14). Inaddition, the prospective Physicians’ Health Study in theUSA following ~86 000 men for over 5 years found menin the highest category for wholegrain breakfast cerealintake (≥ 1 serving/day) had a 20% decreased risk ofdying from CVD, compared to those in the lowest cat-egory [relative risk (RR) of 0.80] (Liu et al. 2003). Nosignificant associations between total or refined break-fast cereal intakes and CVD mortality were found.

One way wholegrain cereals may be having an effecton heart health is the effect of soluble fibre on choles-terol levels. A meta-analysis of 67 controlled studiesfound soluble fibre (2–10 g/day) was associated withsmall but significant reductions in total cholesterol andlow density lipoprotein cholesterol (LDL-C) concentra-tions. No significant difference was seen between solu-ble fibre from oat, psyllium or pectin. There was,however, substantial heterogeneity between studies, sug-gesting the effects of fibre are not uniform. Although inpractical terms, such an effect would be modest (e.g. 3 gof soluble oat fibre could decrease total and LDL-C con-centrations by ~0.13 mmol/L), there is a US-approvedhealth claim for soluble fibre and the risk of CHD (see

Table 14 Wholegrain cereal consumption and decreased risk: prospective cohort studies reviewed by Hu (2003)

Condition SubjectsDecreased risk(adjusted RR) Reference

Stroke 75 521 women 36% (0.64) Liu et al. 2000

CHD 75 521 women 25% (0.75) Liu et al. 1999

Fatal CHD 34 492 women 30% (0.70) Jacobs et al. 1998

Non-fatal heart attack 31 208 men & women 44% (0.56) Fraser et al. 1992

CHD 31 208 men & women 11% (0.89) Fraser et al. 1992

RR, relative risk; CHD, coronary heart disease.

132 Brigid McKevith


section 3.5 for more on health claims) (Brown et al.1999). As well as encouraging consumption of foodsrich in soluble fibre, there may be scope for increasingthe soluble fibre content of cereal products. In the onlyrandomised controlled trial (RCT) using men with a his-tory of myocardial infarction (the Diet and ReinfarctionTrial study), advice to increase cereal fibre had no effecton CHD or all-cause mortality (Ness et al. 2002), butfurther work in healthy individuals is warranted.

Another area of interest is the influence of GI onblood lipids. Two observational studies have shown anegative relationship between GI and high density lipo-protein cholesterol (HDL-C) concentrations, suggestinga low-GI diet may preserve HDL-C levels (Jenkins et al.2002). Several RCTs have shown that, in people withdiabetes, diets containing a large proportion of thedietary carbohydrate as low-GI foods have shownimproved blood lipids, independent of dietary fibreintake (Mann 2001).

There may currently be insufficient evidence to dem-onstrate a cause and effect between heart health andwholegrain foods, but the WHO/FAO stated that therewas a ‘probable’ level of evidence demonstrating NSPand wholegrain cereals decrease the risk of CVD(WHO/FAO 2003). Several health claims in the area ofheart health and wholegrain cereals have been approved(see section 3.5).

3.4.4 Diabetes

Prevention of diabetes A potential role for fibre in theprevention of diabetes was put forward over 30 yearsago, and a high intake of cereal fibre has consistentlybeen associated with a lower risk of diabetes (Willettet al. 2002). For example, in a large prospective study ofmore than 42 000 men followed for about 12 years, aninverse association was found between wholegrainintake and type 2 diabetes. After adjustment for con-founding factors, men in the highest quintile of intakecompared to those in the lowest had an RR of 0.58(Fung et al. 2002). Similar results have been seen inwomen (e.g. Liu et al. 2000; Meyer et al. 2000). Mon-tonen et al. (2003) studied the intake of wholegrain andfibre of over 4 000 Finnish men and women, and thesubsequent incidence of type 2 diabetes during a 10-yearfollow-up. An inverse association was found betweenwholegrain intake and risk of type 2 diabetes, with anRR between the highest and lowest quartiles ofwholegrain consumption of 0.65, i.e. a 42% reductionin risk. A reduced risk of type 2 diabetes was also asso-ciated with cereal fibre (RR 0.39). Data pooled from

seven prospective cohort studies (including the Mon-tonen study) provided a summary estimate of a 30%reduction in risk (RR 0.70) (Liu 2003). In this paper theauthor highlights the need to distinguish between thebiological effects of wholegrain and those of refined-grain products, to help clarify the message that shouldbe communicated to the public.

Several studies have also shown an inverse relationbetween GI/GL and risk of developing diabetes, forexample:

• The Nurses Health Study found for comparing high-est GI with lowest GI, the RR of developing diabeteswas 1.37. The GL was also associated with diabetes (RR1.47), and a high GL combined with a low cereal fibreintake (< 2.5 g/day) increased the risk of diabetes fur-ther (RR 2.50) (Salmeron et al. 1997a).• Similarly, in the Health Professionals’ Follow-UpStudy, men with a high-GI diet had an increased risk ofdiabetes (comparing the highest with the lowest quintile,RR 1.37). Those men with a high-GL diet and a lowcereal fibre intake (< 2.5 g/day) had a further increasedrisk (RR 2.50 compared to men with a low-GL diet andhigh cereal fibre intake) (Salmeron et al. 1997b).

In contrast, The Iowa Women’s Health Study, whiledemonstrating a negative association between cerealfibre intake and risk of diabetes, found no significantassociation between GI or GL and diabetes incidence(Jenkins et al. 2002). However, an elderly cohort wasused in this study, which could have introduced selec-tion bias (Augustin et al. 2002).

Management of diabetes Currently the evidence base isstrong for the role of a high-carbohydrate high-fibre dietin improving glycaemic control for people with type 1 or2 diabetes (Mann 2001) and a higher fibre intake hasbeen associated with better glycaemic control in peoplewith type 1 diabetes (Buyken et al. 1998). A recent RCTdemonstrated that, in people with type 2 diabetes, ahigh-fibre diet (containing 25 g soluble fibre and 25 ginsoluble fibre) could decrease blood glucose and insulinmore than a diet of equivalent macronutrient and energycontent, containing moderate amounts of fibre(Chandalia et al. 2000). It is worth noting that theamount of fibre used in this study (50 g) is high. Thecurrent UK recommendation for adults is 18 g a day andthe average UK intake of fibre in 2000/2001 was 15.2 gfor men and 12.6 g for women (Henderson et al.2003a). Additionally, the method used for measuringfibre in the USA differs from that used in the UK (seesection 3.5.1), making comparisons difficult.

There is also a role for low-GI foods in the manage-



ment of diabetes. Medium-term studies have shown thatimprovements in glycaemic control can be seen whenpeople with diabetes replace high-GI foods with low-GIfoods, such as wholegrain, minimally refined cerealproducts (Willett et al. 2002). For example, a ran-domised, crossover study by Jarvi et al. (1999) demon-strated that a low-GI diet improved glycaemic control aswell as decreasing LDL-C and normalising fibrinolyticactivity compared to a high-GI diet, identical for macro-nutrient composition and amount of dietary fibre.Although long-term studies are required to establish thelong-term consequences, the GI concept is often usedwhen counselling people with diabetes.

3.4.5 Digestive health

Insoluble fibre, which is found in a range of foodsincluding cereals, may be important for gut health.Insoluble fibre absorbs fluid, increasing stool weight. Italso promotes the growth and activity of the gut bacte-ria, which could also be beneficial for gut health.Recently, a small study demonstrated that moderateintakes of high-fibre wheat and high-fibre rye foodscould improve other markers of gut health, such asdecrease faecal beta-glucoronidase, secondary bile acidsand para-cresol concentrations, and decrease faecalpH, compared with a low-fibre diet (McIntosh et al.2003).

From their work in Africa, Burkitt and Walker sug-gested the importance of dietary fibre for digestivehealth, and a role in particular for preventing colorectalcancer. The World Cancer Research Fund currently listsNSP/fibre as a possible factor in decreasing the risk ofcolorectal cancer (World Cancer Research Fund 1997),although a UK report concluded that there was moder-ate evidence that diets rich in fibre would reduce col-orectal cancer (Department of Health 1998). Since thisreport several other studies have been published. Astudy of ~455 000 older women with relatively low fibreintake followed for a mean of 8.5 years found little evi-dence that dietary fibre intake lowered the risk of col-orectal cancer. However, this study was set up toinvestigate breast cancer and not colorectal cancer, andthe highest quintile only had an average fibre intake of~17 g a day (Mai et al. 2003).

Two more recent studies have investigated the intakeof dietary fibre and the incidence of colorectal cancer.The European Prospective Investigation into Cancerand Nutrition (EPIC) study followed more than 50 000subjects aged 25–70 years for almost 2 million person-years. An inverse relationship between dietary fibre infoods and incidence of large bowel cancer was found,

with an adjusted RR in the highest vs. lowest quintileof fibre from food of 0.58 (0.41–0.85). No food sourceof fibre was found to be significantly more protectivebut the results suggested that in populations with alow average intake of dietary fibre, doubling of totalfibre intake from foods could reduce the risk of col-orectal cancer by 40% (Bingham et al. 2003). Anotherstudy performed within the Prostate, Lung, Colorec-tal, and Ovarian Cancer Screening Trial found highintakes of dietary fibre were associated with a lowerrisk of colorectal adenoma, those in the highest quin-tile having a 27% decrease in risk compared to thosein the lowest quintile. Fibre from cereals and fromfruits showed the strongest inverse association (Peterset al. 2003). Intakes in the highest quintiles of thesetow studies were more than 30 g of fibre a day, at leastdouble the current average UK intake. The results fromthese last two studies are in contrast to those of areview of RCTs in this area which found no evidenceto suggest that increased dietary fibre would reduce theincidence or recurrence of adenomatous polyps withina 2–4-year period (Asano & McLeod 2002).

The role of fibre in the treatment of other bowel prob-lems has been investigated. The faecal bulking action ofinsoluble fibre makes it useful in the treatment of con-stipation and diverticular disease (Thomas 1994). In thepast, a high-fibre diet was the normal treatment for irri-table bowel syndrome, but a recent review by Burden(2001) revealed a move-away from this approach,towards manipulation of the fibre fractions in the diet,dependent on the individual’s symptoms.

3.4.6 Other cancers

Fibre may also decrease the risk of pancreatic and breastcancer (WCRF 1997). A series of case–control studies inItaly found an inverse association between wholegrainfood intake and the risk of a range of cancers, includingthose of the upper gastrointestinal tract, the bladder andthe kidney (La Vecchia et al. 2003). Cereals may have aprotective effect on hormone-related cancers because oftheir lignan content (Goldberg 2003). Lignans, a type ofphytoestrogen, are modified by gut bacteria to be moresimilar in structure to mammalian lignans (Truswell2002).

3.4.7 Hypertension

Hypertension or high blood pressure (defined in theguidelines of the European Society of Hypertension as>140/90 mmHg) is a major risk factor for CVD andrenal disease (Hermansen 2000). Changes in sodium

134 Brigid McKevith


intake have been shown to affect blood pressure inolder people and those with hypertension and diabetes,but more recently a food-based approach has beeninvestigated. The Dietary Approaches to Stop Hyper-tension (DASH) studies focused on increasing consump-tion of a range of foods including wholegrain cereals,but with particular emphasis on fruits and vegetables,and low-fat dairy products. The DASH diet demon-strated a strong effect on hypertension, with a decreasein systolic blood pressure (SBP) of 11.4 mmHg and indiastolic blood pressure (DBP) of 5.5 mmHg amongthose hypertensive subjects (n = 133) (Appel et al.1997). The benefits seen with the DASH diet may inpart be due to its high fibre content, and several studieshave specifically looked at the effect of fibre on bloodpressure, for example:

• In a double-blind RCT, dietary fibre given as a sup-plement (7 g/day) was found to significantly reduce DBPamong hypertensive patients (n = 32) compared to thosereceiving a placebo (n = 31) (Eliasson et al. 1992).• A pilot RCT involving 18 hypertensive patients foundthe addition of 5.52 g beta-glucan/day decreased SBP by7.5 mmHg and DBP by 5.5 mmHG. Virtually no changewas seen in the control group (Keenan et al. 2002).• Another small RCT study of hypertenisve patients(n = 88) found that by including a wholegrain oatcereal, more patients in the oats group could stop orreduce their anti-hypertensive medication (77% vs.42%). Those in the oat group whose medication wasnot reduced had substantial decreases in blood pressure,suggesting that wholegrain oats can have a beneficialeffect on blood pressure (Pins et al. 2002).

Although the exact effect (if any) of fibre and/or cere-als on blood pressure is not known, current recommen-dations encourage a whole-diet approach, along withlifestyle modifications such as achieving a healthyweight, regular physical activity, limiting alcohol intake,stop smoking and being physically active. In addition tohelping control blood pressure, these recommendationswill have a wide range of beneficial effects on otherareas of health.

3.4.8 Food intolerance and allergy

There are hundreds of different foods which may causeadverse reactions in certain individuals and cereals con-taining gluten (defined currently by the EU to includewheat, rye, barley, oats and spelt or their hybridisedstrains) are recognised as one of the more commoncauses of intolerance (Buttriss 2002).

A specific intolerance to gluten can cause coeliac dis-ease, which leads to inflammation of the small intestineand malabsorption. In the past the prevalence of coeliacdisease in the UK has been estimated at 1 case in 1 500people. However, the use of serological screening testssuggests the true prevalence may be higher – a study inBelfast has suggested a prevalence of 1 in 130 (Buttriss2002). Traditionally, wheat, rye, barley and oats andproducts containing these cereals have been avoided.However, recently a small study of 15 coeliac diseasepatients in remission, who included large amounts ofoats in their diets, found no adverse effects over a 2-yearperiod (Størsrud et al. 2003). Similarly, work by Jana-tuinen et al. (2002) also found that there were no sig-nificant differences in people with coeliac diseasebetween those consuming oats for 5 years and controls.Although contamination of oats with wheat, rye andbarley during harvesting, transportation and milling ispossible, several studies have reported no effects of traceamounts of gluten, either to the small intestine mucosaor gastrointestinal symptoms.

3.5 Labelling and health claims

3.5.1 Labelling

In the UK, nutrition labelling is not mandatory but if aclaim is made nutrition information must be given. Thetwo current formats are the Group 1 declaration(energy, protein, carbohydrate and fat) and Group 2(as for Group 1 plus sugar, saturates, fibre andsodium). In the UK the Englyst method, which mea-sures only the NSP component, has been used to calcu-late the fibre content of foods. Other EU countries andthe USA use the American Association of AnalyticalChemists (AOAC) method, which also measures ligninand resistant starch, leading to a higher value whencompared with that found using the Englyst method. InDecember 2000, the Food Standards Agency issued anotice to inform the food industry that the AOACmethod would now be used in order to harmonise freetrade.

With regard to ingredient labelling, an amendmenthas been agreed to the EU Directive on food labelling(2000/13/EC). This will require common foods andingredients causing allergic reactions to be labelled –currently some exemptions exist. Cereals containinggluten, i.e. wheat, rye, barley, oats (although this maychange due to new research that is emerging, such asthat mentioned in section 3.4.7), spelt or their hybri-dised strains, and products derived from these foods,will be included in this proposal.



The GI concept (discussed in earlier sections) has beenused in the management of diabetes in a number ofcountries, including Australia where they have devel-oped licensed GI labelling on pre-packaged foods(Nantel 2003). There are several methodological con-siderations in determining the GI of a food, e.g. the risein blood glucose is highest at breakfast (after a 10–12-hovernight fast) and there is variability within andbetween subjects (so tests should be repeated three timeswith each subject to obtain a representative mean).However, there is interest in bringing this concept into aUK public health context and several laboratories willsoon offer GI testing.

3.5.2 Health claims

As more is learnt about diet and health, there is anincreased need and justification to communicate positivehealth messages, and health claims are one method thatmay be used. Although legislation specifically coveringhealth claims does not currently exist in the UK, in theUSA, where there is such legislation, currently approvedclaims include those associating:

• soluble fibre from certain foods and the risk of CHD;• diets low in saturates and cholesterol and high infruits, vegetables and grain products that contain fibre,particularly soluble fibre, with reduced risk of heart dis-ease.

In Sweden, eight generic relationships have been rec-ognised including constipation and dietary fibre, andsoluble fibre and blood cholesterol. In 2002, the UKJoint Health Claims Initiative approved a claim forwholegrain foods and heart health (‘people with ahealthy heart tend to eat more wholegrain foods as partof a healthy lifestyle’), with wholegrain foods defined asthose containing 51% or more wholegrain cereals.

EU legislation on health claims has been proposedwhich potentially will limit the types of foods that willbe allowed to carry claims. As well as prohibitions onnon-specific claims, claims regarding psychological andbehavioural functions and health claims on alcohol,the proposal outlines plans to evaluate the ‘nutritionalprofiles’ of foods, with a view to restricting the use ofclaims on some foods with high fat, high salt and/orhigh sugar contents. A pre-approval process isplanned, which will require submission of a dossiercontaining relevant scientific evidence, prior toapproval of a health claim (further information can befound at http://europa.eu.int/prelex/detail_dossier_real.cfm?CL=en&DosId=184390).

3.6 Consumer understanding

Generally it appears that many consumers believe theirdiet is healthy. For example, in an EU survey, 71% ofrespondents thought they had no need to change whatthey were eating. Additionally, almost half of people didnot think about the nutritional aspects of the foods theyeat (Kearney et al. 1997). It seems that nutrition/healthyeating does not have a top priority for some people(Kearney et al. 2000). Although the UK has no specificrecommendations for servings of wholegrain foods perday, evidence from dietary surveys suggests intakes arelow. For example, about 30% of UK adults had nowholegrain foods during the period of survey (1 week)and over 97% did not meet the US recommendation ofthree servings per day (Lang & Jebb 2003). It has beensuggested that some consumers may find it difficult toidentify wholegrain foods; some people believe they donot have the necessary skills to prepare and cookwholegrain foods while others think wholegrain foodsmay be bland and dry tasting (Lang & Jebb 2003).

Work in Australia found that the relationshipbetween fibre intake and its food sources was relativelywell understood, although confusion still existed aboutspecific food sources of fibre (Cashel et al. 2001). How-ever, it has been shown that it is possible to change con-sumers’ purchasing habits through health promotion.An advertising campaign in the USA highlighting thepossible benefits of a high-fibre, low-fat diet in prevent-ing some types of cancer increased the purchase of high-fibre cereal (Levy & Stokes 1987).

There appears to be a belief among some members ofthe public that carbohydrate-based foods, such ascereals, are high in energy and ‘fattening’, while otherindividuals see these foods as nutritious and good forhealth (Stubenitsky & Mela 2000). High-protein, low-carbohydrate diets are growing in popularity and,although short-term weight loss may occur, this is mostlikely because of decreased energy intake. There is a lackof information regarding the long-term effects of carbo-hydrate restriction and health professionals haveexpressed concerns for people with underlying healthproblems (e.g. CVD, type 2 diabetes and those withimpaired liver and kidney function) (Stanner in press).

In the UK, there appears to be a misconceptionregarding the incidence of allergy and intolerance,including cereals such as wheat, with many more peoplebelieving themselves to have a problem than the evi-dence would suggest. For example, one survey foundthat 20% of adults believed they had a food intolerancewhile in reality food intolerance in total is estimated toaffect 5–8% of children and 1–2% of adults, while the

http://europa.eu.int/prelex/detail_dossier_real

136 Brigid McKevith


prevalence of food allergy is estimated to affect 1–2% ofchildren and less than 1% of adults (Buttriss 2002).

3.7 Key points

• Cereals have been part of the human diet since pre-historic times. They are staple foods, and cereals andcereal products are an important source of energy, car-bohydrate, protein and fibre. They also contain a rangeof micronutrients such as vitamin E, some of the B vita-mins, sodium, magnesium and zinc. Because of the man-datory fortification of some cereal products (e.g. whiteflour and therefore white bread) and the voluntary for-tification of others (e.g. breakfast cereals), they also con-tribute significant amounts of calcium and iron. There isgrowing interest in the phytochemicals cereal foods con-tain and the potential health benefits these substancesmay provide.• There is evidence to suggest that regular consump-tion of cereals, specifically wholegrains, may have arole in the prevention of chronic diseases. The strengthof evidence varies and although cause and effect hasnot currently been established, people who consumediets rich in wholegrain cereals seem to have a lowerincidence of many chronic diseases. It remains to beestablished whether this is a direct effect, or whetherwholegrain consumption is merely a marker of ahealthy lifestyle.• The exact mechanisms by which cereals convey ben-eficial effects on health are not clear but it is likely theyare multifactorial and may be related to their micronu-trient content, their fibre content and/or their GI.• As there may be a number of positive health effectsassociated with eating wholegrain cereals, encouragingtheir consumption seems a prudent public healthapproach. However, as cereals and cereal products con-tribute a considerable proportion of the sodium intakeof the UK population, manufacturers need to continueto reduce the sodium content of foods such as breakfastcereals and breads where possible.• Nutrition labelling is currently not mandatory in theUK, although many manufacturers provide informationvoluntarily. The fibre content of most UK foods is stillmeasured by the Englyst method rather than the AOACmethod used by other EU countries and the USA andnow recommended by the UK’s Food Standards Agency.Currently, UK recommendations for fibre intake relateto the Englyst method, and hence need revision.Changes to EU labelling regulations will see the labellingof common foods and ingredients causing allergic reac-tions, including cereals containing gluten, and the intro-

duction of EU legislation covering health claims mayhelp consumers identify foods with proven health ben-efits.• Several misconceptions exist among the public withregard to cereals and cereal products. Firstly, manymore people believe they have a food intolerance orallergy to these foods than evidence would suggest and,secondly, cereals are seen by some as ‘fattening’. Thepublic should not be encouraged to cut out whole foodgroups unnecessarily. As cereals and cereal productsprovide a range of macro- and micronutrients, eliminat-ing these foods without appropriate support and advicefrom a state-registered dietitian or other health profes-sional could lead to problems in the long term.

4 Future developments

With advances in technology, there are now a number ofways in which cereals and their products can beenhanced. Traditional plant breeding is still an impor-tant tool [e.g. breeding for improved selenium uptakeand/or retention (Lyons et al. 2003)], but it is also pos-sible to change the nutrient content of cereal productsthrough fortification and through genetic manipulationof the crop. Further research into the processing of cere-als and production of cereal products may also improveoverall nutrient content. Another area of interest is theinteraction between genes and nutrients (see section4.3). While technology may provide opportunities, it isimportant to consider the long-term consequences andconsumer acceptability of new technology.

4.1 Fortification

As discussed earlier in section 3.3, flour (except whole-meal) in the UK is fortified with calcium, iron, thiaminand niacin. A number of other cereal products are for-tified voluntarily, with the best example being somebreakfast cereals which are fortified with a range of Bvitamins, vitamin D, iron, vitamin C, vitamin E, beta-carotene and zinc (Buttriss 1999). Although some othercereal products are fortified with folic acid (the man-made form of the B vitamin folate), cereal products inAmerica have been fortified with folic acid by law since1997 and, recently in the UK, there has been debateregarding mandatory fortification of flour with folicacid.

Folic acid supplementation in the early weeks of preg-nancy can protect against neural tube defects (NTD). Allwomen of child-bearing age who may become pregnantare advised to take daily supplements (400 mg) of folic



acid but in 2000/2001 more than 80% of this subgroupof the population had intakes from all sources below400 mg (Henderson et al. 2003b). Additionally, manypregnancies are unplanned. Poor folate status is alsoassociated with high homocysteine levels, an emergingrisk factor for CVD, though it has yet to be demon-strated in RCTs that improvements in folate statusreduce cardiovascular mortality. On the other hand,high intakes of folic acid may mask vitamin B12 defi-ciency, which causes a form of anaemia and is some-times seen in elderly people. Estimates of vitamin B12

deficiency in the over 65s in the UK range from 1 in 500to 1 in 15. If such a deficiency is not identified earlyenough then there is a possible risk of neurological dam-age. However, folate deficiency is also thought to becommonplace in elderly people (NDNS informationfrom 1994/1995 found 1% of men and 6% of womenaged 65 or older had inadequate folate intakes; Finchet al. 1998), posing a real dilemma for public healthpolicy makers.

In America, rates of NTD births fell by 20% in 1 yearand heart attacks among the elderly fell by 3.4% fol-lowing folic acid fortification, but generally there is littleevidence from other countries of the impact of folic acidfortification, especially on the prevalence of vitamin B12

deficiency. In 2000, the UK’s Committee on MedicalAspects of Food proposed that flour be fortified withfolic acid (240 mg folic acid/100 g flour) (Department ofHealth 2000). In 2002, after wide consultation, theFood Standards Agency decided against recommendingmandatory fortification. As more information becomesavailable especially on the risk to those groups with lowvitamin B12 status and the benefits for pregnant womenand possible heart health benefits, this area should berevisited.

4.2 Genetic modification

As well as the possibility of manipulating the expressionof native genes for disease resistance, novel genes mayalso be used, e.g. using virus-derived sequences todevelop virus-resistant plants. It is also possible todevelop transgenic cereals with resistance to herbicides,decreasing the need for herbicide use. Genetic modi-fication also offers the possibility of improving thenutritional properties of cereals. Examples includeincreasing the oligosaccharide, polysaccharide and ironlevels in cereals, enhancing vitamin E levels in corn anddeveloping rice containing beta-carotene and rice con-taining iron (Henry 2001; Khush 2001; Lucca et al.2002).

4.3 Gene–nutrient interactions

Some of the genes involved in the digestion and absorp-tion of carbohydrate have been shown to be polymor-phic or to show rare deficiency variants (e.g. glucose andgalactose malabsorption due to lack of the appropriatetransporter in the small intestine) (Swallow 2003).Although some single genes are being identified, thegenetic component for chronic diseases such as type 2diabetes, heart disease and obesity are mainly multifac-torial (Williams 2003). For example, a subtype of type 2diabetes has been associated with the genetic markersADA and DS20S16 on chromosome 20q and abnormal-ities in the glucokinase gene on chromosome 7p. How-ever, people without either of these genetic linkages canalso have type 2 diabetes (Neel 1999).

As the knowledge base on gene nutrient interactionsgrows, it may be possible to target specific nutritionmessages to people with specific genetic profiles,although such an approach is probably a way off,largely because of the complexity referred to above.With regard to research into nutrition and health,genetic variation is an important consideration and onethat should be addressed in future studies. It has beensuggested that genotyping of subjects in RCTs be per-formed prospectively, allocating subjects of each geno-type randomly to each treatment (Mathers 2003).However, this will add to the complexity of the study,influencing recruitment, study length and cost.

4.4 Key points

• Fortification of white flour with folic acid (the man-made form of the B vitamin folate) has been proposed inthe UK, to decrease the rate of NTD. Such a move couldalso have a benefit for heart health as poor folate statusis associated with high homocysteine levels, an emergingrisk factor for CVD. However, high intakes of folic acidcan mask vitamin B12 deficiency a condition that occursmore frequently with age and has serious neurologicalsymptoms affecting the peripheral nervous system.• The disease resistance of cereal crops can be increasedby manipulating the expression of native genes. Novelgenes may also be used for this purpose as well as fordeveloping cereals with resistance to herbicides, andcereals with improved nutritional properties (e.g.increased levels of iron and rice containing beta-caro-tene). The long-term consequences and consumeracceptability of such advances must be considered andconsumer choice maintained.• Knowledge of the interactions between genes and

138 Brigid McKevith


nutrients continue to grow and in the future it may bepossible to target specific nutrition messages to peoplewith specific genetic profiles.

5 Conclusions and recommendations

Cereals have been a mainstay of the diets of peopleworldwide, since records began. Even with the diversityof foods now available, cereals remain a fundamentalpart of the dietary pattern, providing energy and fibre,and a range of nutrients, such as carbohydrate, protein,B vitamins, vitamin E, iron, magnesium and zinc. For-tified cereal products such as white bread and breakfastcereals are important sources of nutrients for both chil-dren and adults, although sodium levels of these andother processed cereal foods should continue to bereduced to help people to lower their overall sodiumintake.

It is now recognised that cereals can also provideother bioactive substances, such as lignans, which mayprove important for health. Further research is requiredin this area, including identification of other substanceswithin cereals and their bioavailability.

Currently, most of the evidence for the health benefitsof cereal foods relates to wholegrain foods and theirfibre content and/or their low GI, although other factorsmay also be involved (e.g. resistant starch, micronutri-ents and bioactive substances in wholegrain cereals). Toincrease consumption of wholegrain foods, it may beuseful to have a quantitative recommendation. Addi-tionally, a wider range of wholegrain foods that arequick and easy to prepare would help people increasetheir consumption of wholegrain foods.

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Glossary

Caryopsis: the fruit of cereal, commonly referred to asthe grain.

Conditioning: the use of heat in tempering.Couscous: a food product prepared from wheat semo-

lina (T. durum).Decortication: also referred to as dehulling or dehusk-

ing; this process describes the complete or partialremoval of the outer layers from grains (and seeds,fruits and nuts).

Embryo or germ: a thin-walled structure within thecereal grain, containing the genetic material for a newplant.

Endosperm: the main part of the grain, containing thin-walled cells packed with starch.

Fibre: a group of substances in plant foods which can-not be completely broken down by human digestiveenzymes. In the UK the Englyst method has been usedfor determining the amount of fibre in food. Thismethod measures only the polysaccahride componentof dietary fibre, referred to as non-starch polysaccha-rides (NSP), and does not include lignin and resistantstarch. Other countries and the USA use the AmericanAssociation of Analytical Chemists (AOAC) methodwhich also includes lignin and resistant starch.

Glume: an additional layer to the caryopsis, alsoreferred to as the husk.

Glycaemic index (GI): used for classifying carbohydrate-containing foods, GI is the ‘incremental area underthe blood glucose curve after consumption of 50 gcarbohydrate from a test food divided by the areaunder the curve after eating a similar amount of con-trol food (generally white bread or glucose)’ (Ludwig& Eckel 2002).

Glycaemic load (GL): assesses the total glycaemic effectof the diet and is the product of dietary GI and totaldietary carbohydrate.

Goitrogen: substance that inhibits either the synthesis ofthyroid hormones, or the uptake of iodine into thethyroid gland. Goitrogens can be found in food andcan cause goitre when there is a marginal iodineintake.

Gristing: blending of grains prior to milling to producea flour of the required quality.

142 Brigid McKevith


Mycotoxin: toxic chemical substance produced by cer-tain types of mould.

Pearling: A polishing process that removes the outerhusk and part of the grain, leading to rounding of acereal grain.

Phytochemicals: bioactive substances found in plantsand plant-derived foods.

Relative risk (RR): used in epidemiology, it defines thelikelihood of an adverse health outcome in peopleexposed to a particular risk, compared with peoplewho are not exposed.

Resistant starch: starch that resists digestion and is onlypartially digested in the small intestine.

Temper: the addition of water to cereal grain prior tomilling.

Wheat germ: the embryo of the wheat seed which is usu-ally discarded when wheat is milled to white flour.Wheat germ contains most of the lipids of the wheatgrain, most of the vitamin B12, a quarter of the ribo-flavin and a fifth of the vitamin B6.

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